Chapter 6 EMC (Electromagnetic Compatibility)
93
interference of the inverter, and the other is the conduction interference of the inverter.
These two types of interferences cause that the surrounding electric equipments suffer
from the affect of electromagnetic or electrostatic induction. Further,the surrounding
equipment produces error action. For different interferences, please refer to the
following remedies:
1) Generally the meters, receivers and sensors for measuring and testing have more
weak signals. If they are placed nearby the inverter or together with the inverter in the
same control cabinet, they easily suffer from interference and thus generate error actions.
It is recommended to handle with the following methods: away from the interference
source as far as possible; do not arrange the signal cables with the power cables in
parallel and never bind them together; both the signal cables and power cables shall use
shielded cables and shall be well grounded; install ferrite magnetic ring (with
suppressing frequency of 30 to 1,000MHz) at the output side of the inverter and wind it
2 to 3 turns; install EMC output filter in more severe conditions.
2) When the interfered equipment and the inverter use the same power supply, it
may cause conduction interference. If the above methods cannot remove the
interference, it shall install EMC filter between the inverter and the power supply (refer
to Section 6.3.6 for the selection operation) ;
3) The surrounding equipment shall be separately grounded, which can avoid the
interference caused by the leakage current of the inverter's grounding wire when
common grounding mode is adopted.
6-3-5.Remedies for leakage current
There are two forms of leakage current when using the inverter. One is leakage
current to the earth, and the other is leakage current between the cables.
1) Factors of affecting leakage current to the earth and its solutions:
There are the distributed capacitance between the lead cables and the earth. The
larger the distributed capacitance,the larger the leakage current;the distributed
capacitance can be reduced by effectively reducing the distance
between the inverter and the motor. The higher the carrier frequency,the larger the
leakage current. The leakage current can be reduced by reducing the carrier frequency.
However, the carrier frequency reduced may result in
